a. The Field of the Invention
This invention is concerned with the art of coffee-making devices and, more particularly, it is concerned with a coffee-making apparatus of the automatic type and comprising a drum supported for rotation about a generally horizontal axis within an apparatus casing and formed with diametrally opposed coffee-making cavities, each adapted for sequentially operating at three work stations, upon step-by-step rotation of the drum and consecutive indexing alignment with each of said work stations. Said stations comprise a first station wherein a given amount of fresh ground coffee is supplied within the cavity in alignment therewith, a second station wherein the cavity is facing a coffee screening finely perforated diaphragm and wherein pressurized hot water is caused to pass through the ground coffee in said cavity and over the diaphragm to produce the beverage, and a third station whereat the spent coffee is delivered from the cavity and discharged as waste. The drum is rotated step-by-step so that when any individual cavity is standing in alignment with said first station the diametrally opposed cavity stands facing the third station.
The apparatus is complemented with motor means (generally an electric motor) and control means to provide the desired step-by-step rotational sequence at operator command (the apparatus can adapt for coin triggered operation), with water heating, pressurizing and metering means for supplying the proper amount to be percolated at the second station (water amount adjusting means can be provided) as well as a number of operative subassemblies, each comprising a drum and its casing, which can be associated into a multi-unit apparatus for providing beverage amounts at higher rate, than is provided in one multi-unit machine.
B. The prior Art
This art is well known and worked and a large number of machines of the above type have been widely manufactured and sold. The U.S. Pat. No. 3,593,649 is fairly representative of the art and reference is herein made to the disclosure and drawings of such Patent for full understanding of the general structure and operation of said prior machines and, more particularly, of the several corresponding devices thereof and which, are not forming part of the present invention, will not further described.
In said known apparatus the rotary drum (which will be termed "rotor" as this specification proceeds and in the appended claims, the term encompassing the drum structure and the various elements arranged therein and rotated therewith) comprises a body supported and driven for rotation and having a peripheral wall and two generally planar parallel side faces. According to the teaching of such U.S. Pat. No. 3,592,649, the peripheral wall of the drum is cylindrical and co-axial to the axis of rotation and a part-cylindrical perforated diaphragm is secured to the apparatus casing. An improved shape of such drum and diaphragm has been taught in another U.S. Pat. No. 3,872,782, to the present applicant, wherein the drum peripheral wall has the geometrical configuration of a spherical zone having its centre in the axis of rotation and the diaphragm is correspondingly part-spherically shaped.
The rotor of the present coffee-making apparatus can be provided with a drum having either of such configurations and therefore the expression "peripheral wall" referred to the rotor body will encompass both a cylindrical and spherical zone configuration.
In the prior art machines, their rotors each comprise two physically divided diametrally located opposed cylindrical cavities, each open on said peripheral wall of the drum and wherein a piston shaped member is slidably located for urging a layer of ground coffee, during the operation of the machine, against the perforated diaphragm at the second work station and then downwardly pushing the spent coffee into a discharge passage as waste.
During the operation of the prior art machines, the amount of the pressurized hot water is phasedly supplied, at the percolation second station, by feeding the water into the cylindrical cavity facing the diaphragm, at the rear of the piston, which presses the ground coffee against the diaphragm with a force proportional to the water pressure by the cross-sectional area of the cavity, this pressure before percolation being essential for properly producing the beverage. The water is then progressively and slowly transferred through the piston, provided with passages of very small cross-sectional area, into the space which contains the compacted ground coffee, for percolation.
Further, the delivering of the spent coffee as waste is performed at the third station by supplying a further amount of hot pressurized water at the rear of the piston in the cavity which faces an outlet formed in the casing and connected to a duct to waste outlet. Said further amount of water is of the volume defined by the cross-sectional area of the piston, that is, of the cavity, by the stroke of said piston.
Now, according to the essential features of the invention, there have been found that:
a. while the preliminary pressing and compacting of the layer of the ground coffee between the piston and the perforated diaphragm at the second work station is essential, the percolating hot water cannot properly and uniformly find its way through such compacted layer for properly impregnating same and wetting each coffee particle. Further, the coffee swells when impregnated and the percolation becomes more difficult and uneven. A beverage of a great deal better taste can be produced from a proportionally lesser amount of ground coffee if the percolation will be made through a coffee layer subjected to a pressure far less than that necessary for preliminarily compacting of coffee;
b. from the standpoint of cost of operating the apparatus, a not negligible part is that of the energy used for heating the water. The heat supplied to the above said further amount of hot water, made use of for downwardly driving the pistons at the third work station for delivering of the spent coffee to waste is completely wasted too. On the other hand, not water only can be supplied into the rotor for ensuring the proper temperature level of the unit. Therefore it would be desirable to decrease said further amount of heated water.
It is therefore a principal object of this invention to devise and provide a new and improved coffee-making apparatus or machine which is not subject to the above and other limitations and capable of improved operation both to provide a better percolation of a tasteful beverage and with more economical operation.